module 8 bio

Genome

The complete set of genetic information (DNA) in a cell.

Prokaryotic genome

Found in cytoplasm; one circular chromosome + smaller plasmids

Eukaryotic genome

found in nucleus; consists of multiple linear chromosomes (plus circular DNA in mitochondria/chloroplasts).

Chromosome

A tightly coiled structure of DNA and proteins that carries genes.

Chromatin

The uncoiled, thread-like form of DNA found during interphase.

Sister Chromatids:

2 identical copies of a chromosome connected at a centromere.

Homologous Chromosomes

Matching chromosome pairs (one from each parent) that contain the same genes at the same loci but may have different alleles.

Gene

A specific sequence of DNA that codes for a protein.

Allele

Different versions of the same gene that produce variations in traits.

Diploid (2n)

Cells with two sets of chromosomes (one from each parent); e.g., somatic/body cells.

Haploid (n)

Cells with one set of chromosomes; e.g., gametes (sperm & egg).

Karyotype

A picture of all the chromosomes in a cell, used to study number and structure.

Cell cycle:

interphase, G1, S, G2, Mitotic phase (M)

Interphase

The period of growth and DNA replication (G₁, S, G₂). Not part of mitosis.

G1 phase

Cell grows and performs normal functions.

S phase

DNA is replicated

G2 phase

Organelles and proteins are made; cell prepares for mitosis

Mitotic phase

Cell divides into 2 identical cells, includes mitosis and cytokinesis.

Mitosis phases:

prophase, pro-metaphase, metaphase, anaphase, telophase, cytokineses

prophase:

Chromatin condenses into visible chromosomes; spindle forms; nuclear envelope breaks down.

Prometaphase

Nuclear envelope disappears; spindle fibers attach to kinetochores on chromosomes.

Metaphase

Chromosomes line up at the cells equator (metaphase plate)

Anaphase

sister chromatids separate and move to opposite poles

telophase

Chromosomes uncoil; new nuclear envelopes form around each set of chromosomes.

Cytokinesis:

Cytoplasm divides → two identical daughter cells form. (Cleavage furrow in animals, cell plate in plants.)

checkpoints

Control points in the cell cycle that ensure proper division (G₁, G₂, and M checkpoints)

M checkpoint

Ensures all sister chromatids are attached to spindle fibers before separation.

anchorage dependence

Cells must be attached to a surface to divide.

density dependence

cells stop dividing when too crowded

growth factors

External chemical signals that stimulate cell division.

Nondisjunction

Error where chromosomes fail to separate → abnormal chromosome number (e.g., Down Syndrome).

cancer

Uncontrolled cell division due to mutations in regulatory genes.

Type 2 Diabetes (Cell Division Connection)

β cells cannot divide enough to keep up with insulin demand, leading to reduced insulin production.